1. Field of the Invention
This invention relates to improvements in a copying lens comprising four groups disposed substantially symmetrically about a diaphragm.
2. Description of the Prior Art
Generally, copying lenses are required to more faithfully reproduce planar objects than ordinary photographic lenses, and lenses having a small coma and having a good planarity of image plane are desired as such lenses. Moreover, copying lenses are not used at a fixed magnification but at various magnifications and therefore must keep a good performance over a wide magnification range. However, as is well-known, if magnification is changed, lenses usually cannot maintain a performance equivalent to their original image forming performance obtained at the standard magnification. For this reason, various aberration correcting mechanisms involving changing the air spaces between lenses have been devised and these have been successful to some extent in ordinary photographic lenses, but in copying lenses which require strict aberration correction, it has been very difficult sufficiently to correct aberrations.